Method of preparing organo beryllium halides



United States Patent 3,196,187 METHOD OF PREPING GRGANO BERYLLIUMMHZ-DES Giorgio Moretti and Alfredo Turchi, Ferrara, Italy, as-

signors to Montecatini Societal Generale per lindustria Mineraria eChimica, a corporation of Etaly No Drawing. Filed Feb. 12, 1962, Ser.No. 172,788 Claims priority, application Italy, Feb. 15, 1961, 2,734/619 Claims. (Cl. 260-665) The present invention relates to pure organicberyllium compounds and to a method of preparing the same. Moreparticularly, our invention relates to the preparation of compounds ofthe type BeRR in which R is a low molecular weight alkyl radical and Ris a halogen or R.

The methods known from the literature for preparing beryllium dialkylsare based on reactions between metal beryllium and mercury dialkyls orbetween beryllium dihal-ides and Grignard reagents. These processes,however, are impracticable on a commercial scale due to the toxicity ofalkyl mercury compounds and/or because of the requirement of employinglarge amounts of ether (in the reaction between beryllium dihalides andGrignard reagents).

With regard to the preparation of beryllium alkyl halides, the processesknown from the literature involve reacting metal beryllium with alkylhalides or beryllium dihalides with beryllium dialkyls. Such processeslead to very low yields because these reactions take place only withdifficulty.

We have now surprisingly found that beryllium alkyl halides can bereadily obtained in good yields by treat ing beryllium dihalides withapproximately equimolar amounts of aluminium triallryls according to animprovement in the process described in Italian patent application prov.filing No. 8,056/60 (Milan). The beryllium alkyl halides thus formed canbe easily separated from the dialkyl aluminum monohalides that have beenformed.

Particularly suitable beryllium halides include beryllium chloride orbromide. Suitable aluminum trialkyls include aluminum triethyl, aluminumtripropyl and aluminum triisobutyl, and the like.

The reaction between beryllium halides and aluminum trialkyls leads toan equilibrium and therefore beryllium dialkyls are also formed. Thehigher the amount of reacted aluminum trialkyl, the higher is the amountof beryllium dialkyl formed. By operating the amounts of berylliumdihalides and of aluminum trialkyls in molar ratios of about 1:1, i.e.,from about 0.9:1 to 1.121, essentially beryllium alkyl halide areobtained. The aluminum dialkyl monohalide thus formed can be separated,according to our invention, by vacuum distillation or by extraction atroom temperature with a suitable solvent, preferably a low boilingaliphatic hydrocarbon solvent. The relatively non-volatile berylliumalkyl halides, which are virtually insoluble in the solvent at roomtemperature, remain as a residue.

The beryllium alkyl halide can be purified by removing any berylliumdihalides which may be present by extraction with hydrocarbon solventsat their boiling point, followed by cooling to very low temperatureswhereupon the beryllium alkyl halide precipitates. The hydrocarbonsolvent hould preferably be an aromatic solvent.

The solvent used in the extraction must be of sufficient volatility thatit can be removed by evaporation from the beryllium alkyl halide, andmust at the same time exhibit a very low freezing point, so as to permitstrong cooling. A solvent which was found to be particularly suitable istoluene, for it solidifies at a very low temperature and yet issutiiciently volatile.

By the aforementioned process beryllium alkyl halides 3,196,187 PatentedJuly 20, 1955 can be prepared and purified with the obtaining of goodyields.

We have also surprisingly found that from the beryllium alkyl halidesthus prepared, pure beryllium dialkyls can be obtained with good yieldsby reacting such beryllium alkyl halides with a hydride of a metal whichis more electropositive than beryllium, and then adding a suitableolefin which is transformed to the corresponding alkyl. That is, theberyllium alkyl halide reacts with the metal hydride to form a halide ofsuch metal and a beryllium alkyl hydride, which beryllium alkyl hydride,by the addition of an olefin, is transformed into beryllium dialkyl.

Suitable olefins which can be added to the beryllium alkyl-hydrideaccording to our invention are those olefins which will react to form alow molecular weight alkyl radical and include ethylene, propylene,butylene, isobutylene, etc.

The dehalogenation reaction is preferably carried out in the presence ofa solvent or dispersant. Thus, if ethyl ether is used, the berylliumalkyl halide is completely dissolved. In contrast, if a hydrocarbon isused, e.g., toluene, heptane, or the like, only a portion of theberyllium alkyl halide goes into solution and reacts with the metalhydride to form the beryllium alkyl hydride; the beryllium alkyl hydrideis formed, further amounts of beryllium alkyl halide go into solution,until finally all of it has been completely dehalogenated.

The course of the dehalogenation can be controlled by withdrawingsamples of clear liquid and analyzing the halogen present. Thedehalogenation reaction ac cording to our invention is carried out at atemperature of from about 60 to 150 C., and more preferably from aboutto C.

The olefin is easily added to the alkyl beryllium hydride by operatingpreferably under a positive pressure. The addition reaction with theolefin, e.g., ethylene, is carried out at a temperature of from about 50to 80 C., while maintaining a constant pressure of from about 6 to 8atmospheres in the system.

The presence of a halide of the metal which is more electropositive thanberyllium does not disturb the addition reaction of the olefin. Forinstance, by using NaH as the dehalogenating agent, NaCl is formed whichi insoluble in others and hydrocarbons and precipitates as a finelydivided powder. Upon addition of the olefin, a beryllium dialkyl isformed which is completely soluble both in others and hydrocarbons. Byfiltration, centrifuging, or the like, the powdered halide of the metal(the hydride of which was used as the dehalogenating agent) is readilyseparated.

The ether or hydrocarbon solution of beryllium dialkyl can be used as itis or the solvent can be removed by evaporation under a moderate vacuum.The beryllium dialkyl is then distilled under a high vacuum. In suchinstance there is no need to separate the more electropositive metalhalide, for even in its presence one can first remove the solvent andthen distill the beryllium dialkyl under a high vacuum.

If the halogenation has been carried out in the presence of an ether,there is formed a beryllium dialkyl etherate. This etherate is, however,by distillation under a high vacuum, decomposed to produce a berylliumdialkyl which is virtually free of ether.

At the end of the distillation there remains a powder consistingessentially of the more electropositive metal halide and containingsmall amounts of non-dehalogenated beryllium alkyl halide with smallamounts of unreacted metal hydride.

When the desired end product is the beryllium dialkyl, it is notnecessary to purify the beryllium alkyl halide by extraction andcrystallization since the dehalogenation reaction can be carried out onthe raw product obtained by reaction of the beryllium dihalide withaluminum 'trialkyl, after distillation to remove the aluminum dialkylhalide obtained.

The following examples will further illustrate our invention withoutlimiting the scope thereof. All parts are by weight unless otherwiseindicated.

Example 1 106 g. of anhydrous powdered BeCl (corresponding to 1.33moles) are charged under nitrogen into a 1-liter three-necked flaskprovided with a central agitator and a distillation adapter. 165 g. ofAl(C H (1.45 moles) are added dropwise thereto while agitating. When theaddition is completed the flask is agitated for 30 minutes while heatingon an oil bath to 100 C. The mixture is then distilled under a highvacuum (0.01 mm. Hg) by heating the oil bath from room temperature to amaximum of 120 C. 166 g. of distilled product are obtained, and theamounts of Al, Be and Cl contained therein are determined. The productshows 0.093 g. atoms of Be, 1.28 g. atoms of Al and 1.24 g. atoms of C1.

The residue is first treated with anhydrous toluene at room temperaturein order to remove the soluble aluminum product and, after filtration,is then treated with 300 ml. of anhydrous toluene at 110 C. The clearliquid is filtered at a temperature of about 110 C. and is then cooledto 70 C., whereupon beryllium ethyl halide is thus precipitated. Thesolution is siphoned into the flask, the treatment at 110 C. is repeatedand beryllium ethyl chloride is extracted at a temperature of about 110C. and then precipitated at about 70 C. until it has been completelyremoved. The thus crystallized product is dried by heating under vacuumto a final residual pressure of 1 mm. Hg thus obtaining 70.5 g. of

Example 2 51 g. of anhydrous BeCl (0.635 mole) are introduced, underpure nitrogen, into a 250 ml. flask provided with a. distillationcolumnand an agitation system. 74.5 g. of A1(C H (0.653 mole) are thenintroduced. The mixture is agitated and heated to 100 C. for 30 minutes.By successive vacuum distillation, 80.5 g. of product which, byanalysis, shows 0.647 g. atoms of Al and 0.62 g. atoms of C1, areobtained.

The residue, which consists essentially of C H BeCl, is dissolved in 150ml. of anhydrous ether while agitating and is reacted with 30 g. of a52.5% NaH dispersion in mineral oil (0.63 mole of NaH) in a 350 ml.shaking dautoclave kept under agitation at 120 C. for 15 hours. Theautoclave is then cooled, connected with a bottle containing ethylene,and heated to C. The olefin is continuously fed under a constantpressure of about 8 atmospheres for 6 hours. The product is discharged,the autoclave is carefully washed with anhydrous ether, and the whole isconcentrated under vacuum to a final residual pressume of 1 mm. Hg andfinally distilled under a high vacuum. The product distills at 5658 C.(under 0.1 to 0.5 mm. Hg) and weighs 34.7 g. Analysis of this productshows: Be=8.22%; Al=nil. 0.318 g. atoms of Be are therefore present.Yield of organic Be=50%.

Variations can, of course, be made without departing from the spirit ofour invention.

Having thus described our invention, what we desire to secure and claimby Letters Patent is:

1. A method of preparing pure organic beryllium compounds of the formulaBeRX wherein R is alkyl and X is selected from the group consisting ofchloride and bromide, this process comprising alkylating a berylliumdihalide wherein the halogen substituents are selected from the groupconsisting of chloride and bromide with an approximately equimolarquantity of a trialkyl aluminum, the molar ratio of said berylliumdihalide to said aluminum trialkyl being from about 0.911 to 1.111, toform BeRX and a dialkyl aluminum halide wherein the halide substituentis selected from the group consisting of chloride and bromide, andremoving said dialkyl aluminum halide therefrom.

2. The method of claim 1. wherein said removal is effected by vacuumdistilling off of said dialkyl aluminum halide.

3. The method of claim 1 wherein said removal is effected by extractingat room temperature said dialkyl aluminum halide with a low-boilingaliphatic hydrocarbon, then extracting the residue with an aromatichydrocarbon at its boiling point, followed by cooling to therebyprecipitate BeRX.

4; The method of claim 1 wherein R is ethyl.

5. The method of claim 1 wherein said alkylation is carried out at atemperature of from about 20 to C.

6. The method of claim 3 wherein the aliphatic hydrocarbon solvent isheptane.

7. The method of claim 6 wherein the aromatic hydrocarbon is toluene.

8. The method of claim 1 wherein X is chloride.

9. The method of claim 1 wherein the aluminum trialkyl is triethylaluminum.

References Cited by the Examiner UNITED STATES PATENTS 2,786,860 3/57Ziegler et a1. 260448 2,826,598 3/58 Ziegler et al. 260-448 3,061,64710/62 Ienkner 260-429 3,072,697 1/63 Jenkner 260-429 3,103,526 9/63Jenkner 260429 TOBIAS E. LEVOW, Primary Examiner.

1. A METHOD OF PREPARING PURE ORGANIC BERYLLIUM COMPOUNDS OF THE FORMULABERX WHEREIN R IS ALKYL AND X IS SELECTED FROM THE GROUP CONSISTING OFCHLORIDE AND BROMIDE, THIS PROCESS COMPRISING ALKYLATING A BERYLLIUMDIHALIDE WHEREIN THE HALOGEN SUBSTITUENTS ARE SELECTED FROM THE GROUPCONSISTING OF CHLORIDE AND BROMIDE WITH AN APPROXIMATELY EQUIMOLARQUANTITY OF A TRIALKYL ALUMINUM, THE MOLAR RATIO OF SAID BERYLLIUMDIHALIDE TO SAID ALUMINUM TRIALKYL BEING FROM ABOUT 0.9:1 TO 1.1:1, TOFORM BERX AND A DIALKYL ALUMINUM HALIDE WHEREIN THE HALIDE SUBSTITUENTIS SELECTED FROM THE GROUP CONSISTING OF CHLORIDE AND BROMIDE, ANDREMOVING SAID DIALKYL ALUMINUM HALIDE THEREFROM.